I experience it first hand as I am implementing a machine learning algorithm described in a paper. There are questions arising on what and how they did their experiments and on details of the algorithm, which I can't deduce from the paper . Hence, I'm guessing but still unable to reproduce their results. Leaving me to wonder if I have a bug or if I misinterpreted something....
The more interesting question is, how we can check a paper for completeness. I fear the answer is to try and implement it, which is costly for doing it in the peer review process.
